Fluid heat exchange apparatus



Dec. 23, 1941. R. M. HARDGROVE 2,267,027

FLUID HEAT EXCHANGE APPARATUS Filed Feb. 8, 1938 3 Sheets-Sheet l IIIII/IIIIIIIIII INVENTOR.

9; E f, M w? P Dec. 23, 1941. R. M. HARDGROVE 2,267,027

FLUID HEAT EXCHANGE APPARATUS Filed Feb. aflssas Sheets-Sheet 2 INVENTOR.

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Dec. 23, 1941. R. M. HARDGROVE 2,267, 0 27 FLUID HEAT EXCHANGE APPARATUS Filed Feb. 8, 1958 3 Sheets-Sheet 3 Fig]? INVENTOR.

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Patented Dec. 23, 1941 FLUID HEAT EXCHANGE APPARATUS- Ralph M. Hardgrove, Westiield, N. 1., assignor it The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Application February 8, 1938, Serial No. 189,313

2 Claims. (Cl. 257-262) This invention relates to tubular elements and methods of manufacturing the same. It also relates to improvements in furnace structures in which the tubular elements are used.

It is an object of the invention to provide a novel and practical furnace construction which may be advantageously employed in the walls of high temperature furnaces such as the furnaces of modern steam boilers.

More specifically, an object of the invention is to provide a furnace boundary structure employing tubes with toothed metallic. strips helically arranged and welded to the tubes so as to extend 'outwardly therefrom. This forms advantageous means for anchoring a'refractory covering on the tubes and for simultaneously protecting the refractory from overheating during the operation of the furnace at high rates. It also reduces to a high degree the tube stresses caused by the local heating resulting from welding operations. This reduction in tube stresses is important because it eliminates costly stress re- Fig. 9 is a view in the nature of a perspective view showing a modified tube structure.

Fig. '10 is a front elevation of stud tubes with the studs formed fromstrips similar to the strips indicated in the other figures, but having the end studs bent so that they form a barrier or closure between the adjacent wall tubes at positions in, or adjoining, thecenter plane of the tubes.

Fig. '11 is a view in the nature of a transverse section of the embodiment indicated in Fig. 12 of the drawings; i

Fig. 12 is-a fragmentary view in the ature of an elevation of a modified form of the vention.

When the illustrative tube structure is employed in a furnace boundary construction such as that indicated in Fig. l of the drawings the tubes III are held in boundary forming alignment by securement to the support l2. As shown,

lieving operations which may be necessary with other arrangements of simillar elements.

The invention will be more clearly understood,

and other objects of the invention will appear, from the following description which relates to an embodiment of the invention selected for the purposes of illustration. This embodiment of the invention is indicated in the accompanying drawings, in which: a

Fig. 1 is a partial transverse section of a furnace boundary structure including the illustra-- tive tubes and refractory material covering the furnace faces of the tubes and the tube projections formed by the strips.

Fig. 2 is a front elevation of the illustrative tube of the helical strips to the tubes.

Fig. 3 is a rear elevation of the tube shown in Fig. 2.

Fig. 4 is-a transverse section of the illustrative tube structure.

Fig. 5 isan isometric view illustrating a jig and a method of assembly of the strips in the jig,

Fig. 6 is a transverse iertical section through the jig with one of the strips in its operative posltion therein.

Fig. 7 indicates one way in which the strips may.

' structure, particularly showing the relationship be struck or stamped out of a larger strip, 01*

Fig. 8 is a combined elevation and phantom view illustrating the two parts of the forming ,dies

and the formation of the strip resulting from the operation of the dies.

there are internally threaded metallic pads ll welded to the sides of the tubes so as to receive the cap screws I6 extending through openings in the support.

Between the support and the tubes insulating material I8 is placed, and a highly refractory material is installed in a semi-plastic condition over the furnace sides of the tubes and the strips 20 to form the refractory layer 22. This refractory material is mechanically anchored in position by the tubes and the projections of the strips. It is i also thermally maintained by the heat transfer through the strips and their projections to the cooler fluid within the tubes. Externally of the insulating layer i8 is another insulating layer 21 "which operates to-minimize heat losses.

In the manufacture of the tube structure used in the illustrative furnace construction metal strips of the outlines indicated in Fig. 'l are first stamped out of, or struck-from, a larger metal strip or plate 30. Fig. 7 indicates five of the tube strips as being struck from the illustrative portion of the strip 30. Each tube strip is preferably curved as shown, and is formed with two relatively large end projections, and 34 and a number of separate intermediate projections 36 spaced from each other and spaced from the end projections 32 and 34.

It will also be noted that all of the strip projections diverge outwardly away from the baseof the strip which connects the projections.

The material from which the tube strips are formed is preferably steel and the rolled steel plate or strip 3|] is of adequate thickness, preferably not exceeding the wall thickness of th 5 tube.

' plate so as indicated in Fig. '1, they may be fiat, and it is the next step in the illustrative method to form the strips in such a way that they maybe helically arranged on a tube and have their bases fitted closely against the tube surface. This operation may be can-led out indies such as those indicated in Fig. 8. The upper part3! of these dies is preferably movable, and will be herein referred to as the hammer. The lower part 38 is preferably fixed, and will be described as the anvil. The operative faces of the hammer and the anvil are somewhat similar, both having similar projections and indentations toward opposite ends of their strip receiving portions.

When one of the flat strips resulting from the operation indicated in Fig. 7 of the drawings is placed in proper position upon. the anvil 38, and when the hammer 31 is caused to move against the face of the anvil, thestrip and its projections are brought to the positions indicated in dotted lines in Fig. 8. The outer end of the projection 34 is forced downwardly into a shaping cavity in the anvil 38 and the outer end of the projecof either one of these embodimentsof the invention.

In the completion of the illustrative tube structures the above described strip assemblies and then the welder can proceed with the weld- -ing of each strip, forming a continuous weld tion 32 at the opposite end of the strip is forced* upwardly into an indentation in the face of the hammer 31. The spaced projections between the end projections 32 and fl are brought to the intermediate positions indicated in the dotted lines and the base of the strip is formed .to such a curvature that it maybe closely fitted against a cylindrical tube and arranged in a helical man- ..ner thereon.

As a part of the illustrative method, the tube strips resulting from the forming operation gil'di along one side thereof. He can proceedthus from one strip to the other without any further jigging of the strips or loss of time in locating the strips in their proper places. This eliminates the necessity of taking extra time in the field to lay out spacing on the tubes.

After the tubes are completed they may be arranged as indicated in Fig. 1 of the drawings and covered by the highly refractory layer 22 which is preferably solidly tamped 'into position around the strips, their projections, and the tubes.

The practice of this invention results in a reduction of the cost of stud tubes and it affords a method of procedure which permits plain tube water walls to be converted into stud tube constructio'ns, in the field. No injury or impairment of the tubes results from the practice of the method. The strips may be made of stampings of sheet metal, and the cost thus further restrip spacers 50 and 52. These spacers are pro- .vided with strip receiving notches 54 and 55 spaced from each other, and otherwise so related, as to produce the desired spacing ofthe strips and their projections, in the finished tube structure. Difierent elements 50 and 52 with'difierent arrangements of notches may be provided, if different spacings of the tube strip projections are desired.-

The tube'strips are placed in the jig as indi After the desired group of tube strips in the jig is' complete, metallic rods -60 and 62 may be held in contact with the end projections 32 and .34 and tack-welded to the strips. Thereafter, the entire assembly may be lifted from the jig.

It is maintained as an operative unit or assembly until such a time as it is 'to be placed in its final operative position against a tube and welded thereto. The jigging operationmay take place duced. Each strip is of such shape and length thatit matches the face of the plain cylindrical tube along a line defined by a part of a helix.

The condition of universal applicability by means of the use of flame or arc welding equipe mentis met by the fact that each strip has a long continuous edge throughout which the weld metal can be deposited-as easily as if it were a straight line. This ease of welding is also a primary factor contributing to the low cost of the illustrative stud tube construction.

The avoidance of injury to the tube by the welding of the\strips is met by the helical shape of the welded joint, by the limited length of each strip, and by the'serrations which separate the projections of the strip. The serrations. also contribute to the avoidance of, injury during the operation of a furnace in which the invention is employed. Continuous welds at right-angles t o the longitudinal axis of the tubes, or continuous welds parallel tothe longitudinal axis of the in the shop and the assemblies of tube strips packed and shipped to the site of the final in- Y stallation.

To further ininimize and stresses alternate tube sti'ipssuch as the strips 10, I2, and 14 (see Fig. 9) may be end-.wise offsetwith reference to the intermediate strips 16 and 18 during the jigging operation, and before the strips are welded to the rods 80. In this event, theend projections, of the intermediate strips distribute tube 1 In operation, the outeredges of an ordinary ment but this adds ,expense and-is sometimes impractical when tubes are provided with studs."

strip (when welded to the tube-)' are hotter than the inner edges which .have tube wall temperature,

and thusexpand more. A continuous plain strip or fin, will thus stress the tube during operation,

and this stress-is cumulative with reference to the stresses imposed by thewelding, but the strip of'this invention, being serrated on its outer edge, does not'create such'additional stresses.

Fig. of the drawings indicates an embodiment of the invention in which the helical strips 84 have their end projections or studs 88 bent so that they will form a substantial barrier or closure between the tubes 88 and 98. The relationship of these ends to the tubes and the remainder of the strips is particularly well indicated in Fig. 11 of the drawings. With such a cordance with the requirements of the Revised construction, the high temperature side of the wall defined by the tubes 88 and 98 is on the side of the tubes toward which the'studs extend. The opposite sides of the tubes may, in'

The invention having been described in ac- Statutes and particularly sec. 4888, what is claimed as the invention is:.

1. In a tubular structure adapted for use in fluid heat exchange apparatus, a metallic tube, and spaced metallic strips extending over one side of the tube only and secured thereto in good heat exchange relationship, the strips being formed with spaced outwardly extending teeth and being arranged along lines in the nature of helices enclosing the tube, the ends of Fig. 12 of the drawings is an outside elevation of the wall which is indicated in Figs. 10 and 11. It will, of course, be understood that reference to the embodiment of the invention indicated in Figs. 11 and 12 with ceramic refractory material is associated with the tubes and the studs in the same manner as above described with reference to the other illustrative embodiments of the invention. I

The highly refractory material of the layer 22 is held in place firmly because of the shape of the spaces between the helical faces of adjacent strips, which, being warped surfaces around the tubes provide no zone of parallel or outwardly diverging planes, and resist the withdrawal of the interposed refractory. Furthermore, the refractory being positioned as it is, on the opposite sides of a single strip, and extending across the,

spaces of the serrations is held by the strip because the latter is not a flat surface, but rather a warped surface.

It is to be appreciated that, although the invention has been described with reference to the details of particular embodiments thereof, that it is not limited to those details, but is rather of a scope commensurate with the scope of the sub-joined claims.

each strip having wide teeth which are arranged at an angle to the strip and are aligned longitudinally of the tube so as to present structures in the nature of interrupted longitudinal fins along opposite sides of the tube, each fin-like structure being adapted to' co-operate with a similar structure on an adjacent and similar tube to present abacking against which refractory material may be molded, the amount of metal affording heat transfer paths in an annular zone adjacent the tube and the bases of the teeth being greater than the amount of heat transfer metal afforded by the teeth exteriorly of that zone.

2. In a tubular structure adapted for usein fluid heat exchange apparatus, a metallic tube,

and spaced metallic strips extending over one side of the tube only and secured thereto in good heat exch nge relationship, the strips being formed with spaced outwardly extending teeth and being arranged obliquely to the longitudinal axis of the tube, the ends of each strip having wide teeth which are arranged at an angle to the strip and are aligned longitudinally of the tube so as to present structures in the nature of interrupted longitudinal fins along opposite sides of the tube, each fin-like structure being adapted to co-operate with a similar structure on an adjacent and similar tube to present -a backing against which refractory material may be molded, the amount of metal afiording heat transfer paths in an annular zone adjacent the tube and the bases of the teeth being greater than the amount of heat transfer metal afforded by the teeth exteriorly of that zone.

RALPH M. HARDGROVE. 

